Excited to introduce Andromeda XXXVI (And XXXVI)! 🔭
A newly discovered ultra-faint dwarf galaxy near Andromeda, our nearest massive galactic neighbour, and one of its faintest satellites to date arxiv.org/abs/2603.28492 #astronomy #Andromeda #m31 #astrophysics
Figuring out what really counts as a galaxy could give us insights into dark matter and potentially shake up astrophysics, cosmology and particle physics, says columnist Chanda Prescod-Weinstein
A nice write-up of our recent results on the enigmatic Milky Way satellite Ursa Major III/UNIONS 1, which was just published in ApJL! (with @daisybissonette.bsky.social @alexji.bsky.social @mgeha314.bsky.social @joshsimon.bsky.social ++)
Two technicians in clean suits inspect a the completed Roman Space Telescope in a clean room at a NASA assembly facility.
NASA has completed the construction of #NASARoman! Last month, technicians joined the inner and outer portions of the observatory in Maryland.
After final testing, Roman will move to the launch site at the Kennedy Space Center for launch preparations in summer 2026: https://go.nasa.gov/48EqnE8 🔭 🧪
These two plots show the previous work on measuring the velocity dispersion in Ursa Major III/ UNIONS 1 on the left. Including all stars they measure a clear result that would indicate a dark matter halo (orange Gaussian at 3.7 km/s). But these authors noted if one star (a possible binary) was removed, they can no longer resolve this value (dot-dashed curve), making it consistent with no dark matter. Using follow up data, this paper confirms that star is a binary and revises the velocity dispersion (right panel). Now we see it is entirely consistent with no dark matter (gray vertical band). So, *probably* a star cluster!
In Michelle's second paper, she updates us all on the offensively faint Ursa Major III/UNIONS 1 stellar association. Is it a galaxy wtih dark matter or a star cluster? This new paper searches for signs of dark matter and/or binary stars to answer this question! arxiv.org/abs/2510.02431 🔭 ☄️
This looks awesome!
So exciting!!
Interacting galaxies from the Arp-Madore catalog, viewed with the Hubble Space Telescope.
ARP! ARP! ARP! ☄️🔭 arxiv.org/abs/2509.09011
"[Vera] Rubin addressed the [1996] graduating class at the University of California, Berkeley, saying: 'I hope that you will fight injustice and discrimination in all its guises'" 🔭
Looking for a last minute holiday gift?
Mia and the Martians is a new children’s book by myself and @tanyaofmars.bsky.social all about a little girl and her cat, Nebula, who go to Mars for her science fair. They meet the rovers and learn science and emotional lessons from each one
amzn.to/4fvtBuQ
Aaand our next Aeos paper is out as well!!
Jennifer Mead leads the paper, finding feedback blows out all metals from early halos until they reach a mass of about 10^7 Msun. Read it here: arxiv.org/abs/2411.14209
A plot of the brightness (absolute magnitude) of the Milky Way's population of star clusters and dwarf galaxies, as a function of their size (half-light radius). Bright galaxies and clusters occupy distinct regions of this parameter space, but for the faintest objects the two classes overlap so that it is no longer possible to classify a system just from its size and luminosity. Two satellites, Eridanus III and DELVE 1, which have absolute magnitudes of -2 and 0 and sizes of about 7 pc, respectively, are plotted as red diamonds.
🔭 Paper announcement! With @alexji.bsky.social, @wcerny.bsky.social, and a host of others, we analyze some of the first spectroscopy of stars in compact (r < 10 pc), ultra-faint Milky Way satellites in arxiv.org/abs/2410.08276. Our two target systems are highlighted here:
Two-panel image. Left panel: supernova explosion with elements from the periodic table flying out. Right panel: red giant star with pullout showing its atmosphere contains those same elements.
Our paper on the Barbenheimer Star is now published in ApJL! iopscience.iop.org/article/10.3... We at @sdssurveys.bsky.social find evidence for an ancient explosion of an unusually massive star that should have collapsed to a black hole. Thread and 🔭
Image: UChicago/SDSS-V/Melissa Weiss
Okay, this is pretty cool -- Vera Rubin will be on 2025 American quarters!! 🔭 www.usmint.gov/news/press-r...
Stellar density map centered on the new diffuse dwarf galaxy candidate, showing a clear concentration of black points indicative of the dwarf galaxy's presence. At the bottom of the image, an elliptical concentration of stars associated with its host, the LMC-mass galaxy NGC 55, are visible. The satellite appears to be about 1/3 the diameter of its host!
I'm a day late, but I wanted to advertise the latest paper from the DES and DELVE collaborations, led by Mitch McNanna! The paper's results include the discovery of a *very* diffuse (resolved) dwarf galaxy candidate near the LMC-mass host NGC 55 (D ~ 2 Mpc). Read it here:
arxiv.org/abs/2309.04467
It looks promising to me.. I have another one just like this, so maybe we should do go get follow-up data for them :)